Lens unit

ABSTRACT

A lens unit according to the present invention includes: a first lens group and a second lens group being disposed in series on the same optical axis to have a light-converging function, the first lens group and the second lens group each including at least one lens; a first lens barrel  1  retaining the first lens group; a second lens barrel  2  retaining the second lens group and encasing at least a portion of the first lens barrel; and an adjustment mechanism for adjusting relative positioning along an optical axis direction, tilt between respective optical axes, and mutual radial deviation, of the first lens barrel and the second lens barrel.

TECHNICAL FIELD

The present invention relates to a lens unit having a plurality ofoptical lenses, and more particularly to a lens unit which is to be usedfor camera devices and the like and which has excellent assemblability.

BACKGROUND ART

With advancement in technology, digital still cameras (also calleddigital cameras) have rapidly become prevalent, and mobile phones havingintegrated cameras are now commodity. This has led to the increasingneeds for techniques to realize downsized camera devices. Anotherrequirement for camera devices is that images taken with them must havea high image quality.

Generally speaking, a camera device includes a lens unit composed of aplurality of lenses for forming an image on the imaging surface of animaging device. The performance of a camera device, such as resolution,is considerably influenced by the design of a barrel of the lens unit,precision of the parts, precision of assembly when installing thelenses, and so on. Therefore, when assembling a lens unit, attentionmust be paid to the method of adjustment when installing the lenses.

Patent Document 1 discloses a method of interconnecting a plurality oflenses, with their optical axes being adjusted, to produce a lens blockof an integral structure. With reference to FIG. 20 and FIG. 21, theconventional lens block assembly method disclosed in Patent Document 1will be described.

FIG. 20 is a perspective view showing a procedure of inserting lensesinto a fixing jig, and FIG. 21 is a view of a cross section containingthe optical axis of the lenses having been inserted into the fixing jig.As shown in FIG. 20, a first lens 810, a second lens 820, a third lens830, and a fourth lens 840 are sequentially installed into a fixing jig710, such that, as shown in FIG. 21, the lenses, one being stacked uponanother, are supported by the fixing jig 710.

In this state, an adhesive is injected through first throughholes 711A,711B, and 711C, second throughholes 712A, 712B, and 712C, thirdthroughholes 713A, 713B, and 713C, and fourth throughholes 714A, 714B,and 714C penetrating through the fixing jig 710 from its outer surfaceto its inner surface, whereby the first lens 810, the second lens 820,the third lens 830, and the fourth lens 840 are adhesively bonded to oneanother. As a result, a lens block with the four integral lenses iscompleted. According to Patent Document 1, radial deviation of thelenses can be adjusted by inserting a jig rod into each throughhole andmoving the lenses before the adhesive bonding. The assembled lens blockis fixed to a barrel of the camera device.

On the other hand, Patent Document 2 and Patent Document 3 disclosemethods where radial deviation of lenses with respect to a lens barrel710 is adjusted by inserting a jig via throughholes like the firstthroughholes 711A, 711B, and 711C, second throughholes 712A, 712B, and712C, third throughholes 713A, 713B, and 713C, and fourth throughholes714A, 714B, and 714C shown in FIG. 20 and FIG. 21.

CITATION LIST Patent Literature

-   [Patent Document 1] Japanese Laid-Open Patent Publication No.    2007-94241-   [Patent Document 2] Japanese Laid-Open Patent Publication No.    2007-187776-   [Patent Document 3] Japanese Laid-Open Patent Publication No.    2004-85706

SUMMARY OF INVENTION Technical Problem

However, using the method disclosed in Patent Document 1 or the methodsdisclosed in Patent Documents 2 and 3 to adjust the radial deviation ofthe lenses each time would detract from workability, and makes itdifficult to adjust the radial deviation of the lenses with a highprecision. Moreover, there are limits to decreasing the radial deviationof the lenses toward obviating adjustments.

Moreover, higher and higher-precision optics are desired in recentyears, making it necessary to adjust not only the radial deviation ofthe lenses, but also intervals between the lenses and their tilts andthe like; otherwise, it would be difficult to attain satisfactoryperformance.

The present invention is meant to solve at least one of suchconventional problems, and aims to provide a lens unit which permitshigh-precision adjustment of lens positions and the like by a simplemethod, and which ensures stable performance.

Solution to Problem

A lens unit according to the present invention comprises: a first lensgroup and a second lens group being disposed in series on a same opticalaxis to have a light-converging function, the first lens group and thesecond lens group each including at least one lens; a first lens barrelretaining the first lens group; a second lens barrel retaining thesecond lens group and encasing at least a portion of the first lensbarrel; and an adjustment mechanism provided in a region of the firstlens barrel and the second lens barrel where the second lens barrelencases at least a portion of the first lens barrel, the adjustmentmechanism being for adjusting at least one of: relative positioningalong an optical axis direction, tilt between respective optical axes,and mutual radial deviation, of the first lens barrel and the secondlens barrel.

In a preferred embodiment, for adjusting the relative positioning alongthe optical axis direction and the tilt between the respective opticalaxes, the adjustment mechanism includes at least one adjustment pinsupported by the second lens barrel so as to be capable of pivoting, andat least one adjustment groove located on an outer surface of the firstlens barrel; the at least one adjustment pin includes a guide axisportion of a cylindrical shape whose center defines a guide axis centeraround which the pivoting is to occur, and an eccentric portion havingan eccentric axis center which is eccentric from the guide axis centerand having, in at least a portion thereof, a circular cross sectioncentered around the eccentric axis center; the guide axis portion isinserted in a guide hole so as to be capable of pivoting, the guide holehaving an axis center along a radial direction of the second lensbarrel; the eccentric portion is engaged in the at least one adjustmentgroove of the first lens barrel; and when the at least one adjustmentpin is pivoted around the guide axis portion, a portion of the at leastone adjustment groove abutting with the eccentric portion moves alongthe optical axis direction.

In a preferred embodiment, the adjustment mechanism includes three eachof said at least one adjustment pin and said at least one adjustmentgroove; and the three adjustment pins are disposed on an outer surfaceof the second lens barrel at an interval of 120 degrees centered aroundthe optical axis.

In a preferred embodiment, when the three adjustment pins aresimultaneously pivoted in a same direction and with a same velocity, thefirst lens barrel is moved relative to the second lens barrel inparallel to the optical axis direction; and when at least one of thethree adjustment pins is pivoted in a different direction or with adifferent velocity from that of any other, the optical axis of the firstlens barrel is tilted with respect to the optical axis of the secondlens barrel.

In a preferred embodiment, the eccentric portion of each adjustment pinhas a bloated barrel surface in at least a portion thereof, theeccentric portion achieving point contact with the adjustment groove ata portion of the bloated barrel surface.

In a preferred embodiment, for adjusting mutual radial deviation betweenthe first lens barrel and the second lens barrel, the adjustmentmechanism further includes at least one adjustment screw and at leastone loading spring, the at least one adjustment screw being supported bythe second lens barrel so as to be capable of pivoting; the at least oneadjustment screw includes a ridged screw portion, a screw head portionlocated at one end along an axial direction, and a pressurizing bulgelocated at another end along the axial direction; the screw portion isscrewed into a screw hole, an axial direction of the screw hole being aradial direction in a cross section of the second lens barrel that isperpendicular to the optical axis; the pressurizing bulge abuts againsta screw abutment face provided on an outer surface of the first lensbarrel, the screw abutment face being orthogonal to an axis center ofthe at least one adjustment screw; and the at least one loading springis coaxial with the at least one adjustment screw supported by thesecond lens barrel, and presses the first lens barrel from the secondlens barrel toward the optical axis of the first barrel.

In a preferred embodiment, the first lens barrel moves relative to thesecond lens barrel in a direction in which the adjustment screw proceedswhen the adjustment screw is pivoted in the screw hole.

In a preferred embodiment, the adjustment mechanism includes two each ofsaid at least one adjustment screw and said at least one loading spring;and the two adjustment screws, respectively, and the two loadingsprings, respectively, are located on two lines orthogonallyintersecting at a point on a plane which is perpendicular to the opticalaxis of the first lens barrel and at which the optical axis is located.

In a preferred embodiment, the pressurizing bulge of each adjustmentscrew has a hemispheric portion, the hemispheric cross-sectional portionabutting against the screw abutment face; and the first lens barrelmoves relative to the second lens barrel in a direction in which theadjustment screw proceeds when the adjustment screw is pivoted in thescrew hole.

In a preferred embodiment, among tolerances in lens assembly concerningan entire lens optics including the first lens group and the second lensgroup, a tolerance in assembly for satisfying a required performancebetween a lens of the first lens group installed in the first lensbarrel that is located the closest to the second lens barrel and a lensof the second lens group installed in the second lens barrel that islocated the closest to the first lens barrel is smaller than a tolerancein assembly between any other lenses.

Advantageous Effects of Invention

In accordance with a lens unit of the present invention, after therespective lenses are mounted in the first lens barrel and the secondlens barrel, positioning along the optical axis direction, tilt of theoptical axes, and radial deviation between the first lens barrel and thesecond lens barrel can be adjusted anew, whereby a lens unit with anincreased precision can be constructed.

Moreover, in accordance with a lens unit of the present invention, sincean adjustment pin for adjusting the position of the first lens barrelrelative to the second lens barrel along the optical axis direction isprovided, it is possible to adjust the position of first barrel relativeto the second barrel along the optical axis direction with a simpleconstruction.

Moreover, in accordance with a lens unit of the present invention,adjustment pins are provided in three places at an equal interval,thereby allowing the position of the first lens barrel relative to thesecond lens barrel along a direction which is parallel to the opticalaxis, and the tilt therebetween, to be both adjusted.

Moreover, in accordance with a lens unit of the present invention, thefirst lens barrel can smoothly operate with respect to the adjustmentpins, based on a construction where the adjustment pins are in pointcontact with the adjustment grooves.

Moreover, in accordance with a lens unit of the present invention, sinceadjustment screws are provided for adjusting the positions of the firstlens barrel relative to the second lens barrel along a radial direction,it becomes possible to make an eccentricity adjustment of the firstbarrel relative to the second barrel with a simple construction.

Moreover, in accordance with a lens unit of the present invention,adjustment screws are provided in two places on mutually orthogonalaxial lines, thus allowing the position of the first lens barrelrelative to the second lens barrel to be moved along each of biaxialdirections, whereby movements in any direction orthogonal to the opticalaxis are enabled.

Moreover, in accordance with a lens unit of the present invention, at ahemispheric portion which is at one end face, each adjustment screwabuts against a bearing plane. Therefore, even when the tilt angle ofthe adjustment screw with respect to the first lens barrel changes, thestate of abutment does not significantly change; as a result,adjustments of the first lens barrel relative to the second lens barrelwith the adjustment pins can also occur smoothly.

Moreover, in accordance with a lens unit of the present invention, amongthe errors to occur when installing the lenses, a smaller amount oftolerance is allowed for the assembly error between the first lensbarrel and the second lens barrel than for the assembly error of anyother lens. Thus, it is possible to perform a high precision adjustmentonly at the assembly step between the first lens barrel and the secondlens barrel, while relaxing the precision of adjustment in the assemblystep of any other lens. This makes it possible to reduce the number ofadjustment steps, and also improve the entire lens unit to higher levelsof perfection.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A perspective view showing the entirety of an embodiment of alens unit according to the present invention.

FIG. 2 An exploded perspective view of a first lens barrel of a lensunit of an embodiment.

FIG. 3 An exploded perspective view of a second lens barrel of a lensunit of an embodiment.

FIG. 4 A unit exploded perspective view of a lens unit of an embodiment.

FIGS. 5 (a) and (b) are a front view of a lens unit of an embodiment anda cross-sectional view at position A-A of the view shown in (a).

FIG. 6 Another unit exploded perspective view of a lens unit of anembodiment.

FIGS. 7 (a), (b), and (c) are a perspective view, front view, and across-sectional view of an adjustment pin of an embodiment.

FIG. 8 A perspective view showing how an adjustment pin of an embodimentmay be installed.

FIG. 9 (a) is a side view of a lens unit of an embodiment; and (b) is across-sectional view at position B-B of the view shown in (a).

FIG. 10 (a) is a side view of a lens unit of an embodiment; and (b) is across-sectional view at position B-B of the view shown in (a).

FIG. 11 An enlarged cross-sectional view of the neighborhood of anadjustment pin of a lens unit of an embodiment.

FIG. 12 A perspective view of the entire lens unit of an embodiment.

FIG. 13 (a) is an exploded perspective view of a lens unit of anembodiment; and (b) is an enlarged perspective view of the neighborhoodof a recess of the first lens barrel.

FIG. 14 A perspective view showing how a second adjustment screw of anembodiment may be installed.

FIG. 15 (a) is a side view of a lens unit of an embodiment; and (b) is across-sectional view at position B-B of the view shown in (a).

FIGS. 16 (a), (b), and (c) are a perspective view and a front view of avariant of the adjustment pin of an embodiment, and a cross-sectionalview at position A-A of the view shown in (b).

FIGS. 17 (a) and (b) are a side view of an embodiment of a lens unit inwhich adjustment pins as shown in FIG. 16 are used and a cross-sectionalview at position F-F of the view shown in (a).

FIGS. 18 (a), (b), and (c) are a perspective view and a front view of afurther variant of the adjustment pin of an embodiment, and across-sectional view at position A-A, of the view shown in (b).

FIGS. 19 (a), (b), and (c) are a perspective view and a side view of anembodiment of a lens unit in which adjustment pins as shown in FIG. 17are used, and a cross-sectional view at position F-F of the view shownin (b).

FIG. 20 An exploded perspective view showing lenses having beenassembled in a lens barrel, in a conventional lens unit.

FIG. 21 A cross-sectional view showing lenses having been assembled in alens barrel, in a conventional lens unit.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of a lens unit according to the presentinvention will be described.

First, with reference to FIG. 1 to FIG. 5, the overall construction ofthe lens unit will be described.

As shown in FIG. 1, a lens unit 100 includes a first unit 10 and asecond unit 20.

As shown in FIG. 2, the first unit 10 includes: a first lens barrel 1;and a first group of lenses each of which is inserted into the firstlens barrel 1, i.e., a first lens 11, a second lens 12, and a third lens13.

As shown in FIG. 3, the second unit 20 includes: a second lens barrel 2and a second group of lenses each of which is inserted into the secondlens barrel 2, i.e., a fourth lens 24 and a fifth lens 25; a spacer 26;and a lens retainer 27. The spacer 26 defines an interval between thefourth lens 24 and the fifth lens 25. The lens retainer 27 prevents thefourth lens 24 and the fifth lens 25 from dropping out of the secondlens barrel 2. The second lens barrel 2 has an inner surface whichcontains at least a portion of the first lens barrel 1. The first lensgroup and the second lens group are disposed in series on the sameoptical axis, thus exhibiting a predetermined light-converging functionwhich is required of the lens unit 100.

After the respective lenses are inserted as shown in FIG. 4, the firstunit 10 is inserted into the second barrel 2 of the second unit 20. Analignment guide recess 1R is provided in the first lens barrel 1, whilean alignment guide bump 2R is provided on the second lens barrel. Thealignment guide recess 1R and the alignment guide bump 2R fit together,whereby the alignment of the angular positions of the lens barrels alongthe direction of rotation is uniquely determined. FIGS. 5( a) and (b)are a front view and a cross-sectional view of the lens unit 100 havingbeen assembled in this manner.

Next, the reason why the first unit 10 and the second unit 20 are splitwill be described. Generally speaking, in a lens unit lacking a zoomdriving or focus driving mechanism, when lenses are installed into alens unit, all lens are to be sequentially installed into a single lensbarrel. Under specifications such that high precision in position is notrequired between lenses, offsets of lenses with respect to the lensbarrel are tolerated within the range of precision variation of theouter finished dimensions of each lens and the lens barrel. However,when the offsets of the lenses with respect to the lens barrel are nottolerated even within the range of precision variation of the outerfinished dimensions of each lens and the lens barrel, the amounts ofoffset need to be fine-adjusted. In this case, each time one lens isinstalled, while measuring the reflection eccentricity, MTF (ModulationTransfer Function), and the like of each lens, the lens positions areadjusted so that the optical axis of those lenses which have alreadybeen inserted coincides with the optical axis of the lens which is justinsert.

However, in the case where the required precision is high, such a methoddoes not allow the optical axes of the lenses to coincide with asufficiently high precision. In this case, the aforementioned method isfollowed, or the required precision is even lowered for the installationof each lens, while special adjustments are intensively made for some ofthe lenses. In other words, within the lens unit, lenses to beintensively subjected to a high precision adjustment are separated fromother lenses, and then the adjustments are made.

In the present embodiment, the lens unit includes five lenses, forexample. The optics is designed so that the lens optics will attain ahigh-precision performance throughout the entire lens unit when theoptical axes of the third lens 13 and the fourth lens 24 above all,preferably, are adjusted with a high precision. In other words, amongthe tolerances in lens assembly concerning the entire lens unit, thetolerance in assembly for satisfying the required performance betweenthe lens of the first lens group installed in the first lens barrel 1that is located the closest to the second lens barrel 2 and the lens ofthe second lens group installed in the second lens barrel 2 that islocated the closest to the first lens barrel 1 is smaller than thetolerance in assembly between any other lenses. Therefore, the lens unitoptics is split between the first unit 10, in which the first lens 11,the second lens 12, and the third lens 13 are installed, and the secondunit 20, in which the fourth lens 24 and the fifth lens 25 areinstalled, and the offset and tilt between the optical axes of the thirdlens 13 and the fourth lens 24, as well as the interval between theselenses, are adjusted with a high precision.

Although the first unit 10 includes three lenses and the second unitincludes two lenses in the present embodiment, it suffices if the firstunit 10 and the second unit 20 each includes at least one lens.Moreover, it is preferable that, among the plurality of lenses composingthe lens unit, plural lenses are allocated in the first unit 10 and thesecond unit 20 in such a manner as to enable adjustment between theoptical axes of two adjacent lenses that most significantly affect theoptical performance of the lens unit optics, as described above. Forexample, in the case where the lens unit includes seven lenses, suchthat the offset between the optical axes of the third and fourth lensesexerts more influence on the performance of the entire lens unit opticsthan does the offset between the optical axes of any other lenses, it ispreferable to allocate the first to third lenses in the first unit 10and fourth to seventh lenses in the second unit 20. When the first lensgroup and the second lens group are designed so as to have such opticalcharacteristics, it becomes possible, by using the lens unit of thepresent embodiment, to adjust the lens positions so that the opticalperformance of the entire lens unit becomes highest, through a simplemethod.

However, the present invention is not limited to the case where thetolerance in lens assembly between two adjacent lenses from the firstlens group and the second lens group is the smallest. For example, adesign may be adopted where the two adjacent lenses having the smallesttolerance in lens assembly are disposed so as to sandwich a spacer 26therebetween, such that the spacer 26 helps the alignment error to fallwithin the tolerance in lens assembly. Without being limited to a spacer26, a design may be adopted where any other means that is provided inthe lens unit ensures that the alignment error falls within thetolerance in lens assembly. In this case, even under a design such thatthe tolerance in lens assembly between two adjacent lenses from thefirst lens group and the second lens group has the second lowest value,it is possible to adjust the lens positions so that the opticalperformance of the entire lens unit becomes highest. Moreover, in thecase where no other alignment means is provided in the lens unit, andthe tolerance in lens assembly between two adjacent lenses from thefirst lens group and the second lens group is not the smallest, at leastthe alignment and adjustment of the tilt between the optical axes of thefirst lens group and the second lens group can be performed in a simplemanner, thus making the lens assembly easier than conventional.

Next, a method of adjusting a tilt between the optical axis of the firstunit 10 and the optical axis of the second unit 20, and the positions ofthe two along the optical axis direction, will be described withreference to FIG. 6 to FIG. 10.

As shown in FIG. 6, as an adjustment mechanism, the lens unit has afirst adjustment pin 31, a second adjustment pin 32, and a thirdadjustment pin 33. Moreover, it also has a first adjustment groove 1A, asecond adjustment groove 1B, and a third adjustment groove 1C providedin the first lens barrel 1. The first adjustment pin 31, the secondadjustment pin 32, and the third adjustment pin 33 are respectivelyinserted into the first adjustment groove 1A, the second adjustmentgroove 1B, and the third adjustment groove 1C of the first lens barrel1, while being supported so as to be capable of rotating (axiallysupported) by a first guide hole 2A, a second guide hole 2B, and a thirdguide hole 2C which are provided in the second lens barrel 2.Hereinafter, the first adjustment pin 31, the second adjustment pin 32,and the third adjustment pin 33 may be collectively referred to asadjustment pins.

The reason why adjustment pins are provided in three places is that,once three places are determined, the attitude of the first unit 10 willbe uniquely determined. If two places are determined, there will be somefreedom left; if four places, there will be too much restriction. Thus,three places is optimum. However, even in the case of one place, twoplaces, or five or more places, it is possible to adjust the adjustmentof the tilt between the optical axes of the first lens barrel and thesecond lens barrel and their positions along the optical axis direction.Preferably, the adjustment pins are provided in three places on theouter surface of the second lens barrel 2, at an interval of 120 degreescentered around the optical axis of the second lens barrel 2.

FIG. 6 illustrates the first lens barrel 1 being disengaged from thesecond lens barrel 2 in order to clearly show how the first adjustmentpin 31, the second adjustment pin 32, and the third adjustment pin 33relate to the first adjustment groove 1A, the second adjustment groove1B, and the third adjustment groove 1C; however, the first lens barrel 1is actually partially inserted in the second lens barrel 2, and is heldin place according to each association line shown in FIG. 6.

FIGS. 7( a), (b), and (c) are a, perspective view, a front view, and across-sectional view showing the shapes of the first adjustment pin 31,the second adjustment pin 32, and the third adjustment pin 33. Each ofthe first adjustment pin 31, the second adjustment pin 32, and the thirdadjustment pin 33 has a guide axis portion 3A, an eccentric portion 3B,and a manipulating portion 3C, these having an essentially cylindricalshape, for example. Perpendicularly to the direction in which thecylindrical shape extends, the manipulating portion 3C has the largestcross section, followed by the guide axis portion 3A and then by theeccentric portion 3B in descending order of cross-sectional area. As aresult, there are stepped portions at boundaries between adjoiningportions. As shown in FIG. 7, the eccentric axis center of the eccentricportion 3B is eccentric, by an eccentricity G3AB, with respect to theguide axis center of the guide axis portion 3A. Note that themanipulating portion 3C is disposed coaxially with respect to the guideaxis portion 3A.

Moreover, a tip 3D of each adjustment pin has a bloated barrel surface,with a cross-sectional shape which is a curved cross section as shown inFIG. 7. At the tips 3D, the first adjustment pin 31, the secondadjustment pin 32, and the third adjustment pin 33 are in point contactwith the respective bottoms of the first adjustment groove LA, thesecond adjustment groove 1B, and the third adjustment groove 1C.

FIG. 8 specifically shows a position at which the second adjustment pin32 is inserted into the second adjustment groove 1B. FIGS. 9( a) and (b)are a side view, and a cross-sectional view along a direction which isorthogonal to the optical axis direction, showing the first adjustmentpin 31, the second adjustment pin 32, and the third adjustment pin 33having been installed. FIGS. 10( a) and (b) are a side view, and across-sectional view along a direction which is parallel to the axialdirection, of the same. FIG. 11 is a detailed enlarged view of theneighborhood of the second adjustment pin 32 in FIG. 10.

As shown in FIG. 6, FIG. 8, FIG. 9, FIG. 10, and FIG. 11, each of thefirst adjustment groove 1A, the second adjustment groove 1B, and thethird adjustment groove 1C extends along the circumferential direction,and is provided in a portion of the outer surface of the first lensbarrel 1. Moreover, as will be seen from FIG. 11, the adjustment groovewidth should be such that the tip 3D provided on the second adjustmentpin 32 is insertable, and preferably, there is minimum play betweenthem, i.e., the interspace between the inner surface of the secondadjustment groove 1B and the tip 3D is as small as possible.

The guide axis portion 3A provided on the second adjustment pin 32 isaxially supported so as to be capable of rotating, by the second guidehole 2B provided on the second barrel 2, such that the eccentric portion3B and the tip 3D are eccentric with respect to the guide axis portion3A. Therefore, when the second adjustment pin 32 rotates in an arrowD32R direction in FIG. 1, the second adjustment groove 1B moves in anarrow D32L direction. The rate of the resultant amount of move is theeccentricity G3AB per rotation by 360 degrees. The eccentricity G3ABdefines the maximum adjustable dimension of the second adjustment groove1B.

Although the construction of the second adjustment pin 32 has beendescribed as an example, the first adjustment pin 31 and the thirdadjustment pin 33 accordingly have a similar construction.

The action of such structure will be described with reference to FIG.12. The tilt (angle) between an optical axis a10 of the first unit 10(and the first lens barrel) and an optical axis a20 of the second unit20 (and the second lens barrel) is uniquely determined when the firstadjustment groove 1A, the second adjustment groove 1B, and the thirdadjustment groove 1C become aligned with the first adjustment pin 31,the second adjustment pin 32, and the third adjustment pin 33.

At this time, as shown in FIG. 12, if only one of the first adjustmentpin 31, the second adjustment pin 32, and the third adjustment pin 33 isindividually rotated along the arrow D31R direction, the arrow D32Rdirection, or the arrow D33R direction, the first adjustment groove 1Awill move along the arrow D31L direction, the second adjustment groove1B along the arrow D32L direction, and the third adjustment groove 1Calong the arrow D33L direction, each alone by itself. As a result ofthis, the first unit 10 will be tilted respectively in an arrow D31Tdirection, a D32T direction, or a D33T direction. By utilizing thisprinciple, the tilting angle of the optical axis a10 of the first unit10 with respect to the optical axis a20 of the second unit 20 can beadjusted.

Rather than manipulating each adjustment pin alone, an appropriateallocation of amounts of adjustment may be used, which enables anyarbitrary angle to be set. For example, by pivoting all of the firstadjustment pin 31, the second adjustment pin 32, and the thirdadjustment pin 33 simultaneously in the same direction and with the samevelocity, the first lens barrel 1 will move in parallel to the opticalaxis direction from the second lens barrel 2. Moreover, by allowing atleast one of the three adjustment pins to pivot in a different directionor with a different velocity from the others, the optical axis a10 ofthe first lens barrel 1 will be tilted from the optical axis a20 of thesecond lens barrel 2.

Thus, when different amounts of adjustment are applied to the firstadjustment pin 31, the second adjustment pin 32, and the thirdadjustment pin 33, their angles with the first adjustment groove 1A, thesecond adjustment groove 1B, and the third adjustment groove 1C willchange in time during the adjustment step; however, as already describedabove, the tip 3D of each adjustment pin has a curved cross section toachieve point contact, thus enabling unhindered, smooth adjustment.

As shown in FIG. 13( b), end faces of the alignment guide recess 1Rprovided in the first barrel 1 preferably have a curved surface shape.As a result, when adjusting the tilt of the first unit 10 with respectto the second unit 20, alignment along the direction of rotation can beeasily maintained without causing interference between itself and thealignment bump 2R provided on the second barrel 2.

Furthermore, when all adjustment pins are simultaneously manipulated bythe same amount, the differences in axial position of the first unit 10and the second unit 20 between portions where the adjustment pins areadjusted do not change, i.e., the tilting angle between the optical axisa10 of the first unit 10 and the optical axis a20 of the second unit 20does not change; and yet, the axial dimension between the first unit 10and the second unit 20 changes. By utilizing this principle, the axialposition of the first unit 10 with respect to the second unit 20 can beadjusted.

Although the present embodiment illustrates the separated firstadjustment groove 1A, second adjustment groove 1B, and third adjustmentgroove 1C as shown in FIG. 9, it will be appreciated that acircumferential adjustment groove which is entirely continuous along thecircumferential direction will serve a similar function, for example.

Next, a method of adjusting a radial deviation of the first unit 10 withrespect to the second unit 20 along a direction which is orthogonal tothe axial direction, i.e., a radial deviation between the optical axisa10 and the optical axis 20, will be described with reference to FIG. 13to FIG. 15.

As shown in FIG. 13 to FIG. 15, as an adjustment mechanism, the lensunit includes a first adjustment screw 41 and a second adjustment screw42, and a first loading spring 43A and a second loading spring 44A whichprovide reaction forces against the first adjustment screw 41 and thesecond adjustment screw 42. In the present embodiment, a first springretainer 43B and a second spring retainer 44B for retaining the firstloading spring 43A and the second loading spring 44A are furtherprovided. The first adjustment screw 41 and the second adjustment screw42 each include a threaded screw portion, a screw head portion providedat one end of the axial direction, and a pressurizing bulge provided atthe other end.

As shown in FIG. 13, the screw portions of the first adjustment screw 41and the second adjustment screw 42 are engaged in a first adjustmentscrew hole 2D and a second adjustment screw hole 2E which are providedin the second lens barrel 2, thus achieving abutment against a firstscrew abutment face 1D and a second screw abutment face 1E provided onthe first lens barrel 1.

Moreover, by means of screws or the like, the first spring retainer 43Band the second spring retainer 44B are fastened into a first springfixing hole 2F and a second spring fixing hole 2G which are provided inthe second lens barrel 2, while pressing the first adjustment spring 43and the second adjustment spring 44 against a first spring-pressed face1F and a second spring-pressed face 1G which are provided on the firstlens barrel 1.

The first adjustment spring 43A and first adjustment spring retainer43B, and the second adjustment spring 44A and second adjustment springretainer 44B, are provided, respectively, at positions which are on theaxes of the first adjustment screw 41 and the second adjustment screw 42and which oppose the first adjustment screw 41 and the second adjustmentscrew 42 with respect to the optical axis of the second lens barrel 2.Moreover, the first adjustment screw 41, first adjustment spring 43A andfirst adjustment spring retainer 43B, and the second adjustment screw42, second adjustment spring 44A and second adjustment spring retainer44B, are disposed respectively on two lines orthogonally intersecting ata point which is on a plane perpendicular to the optical axis a10 of thefirst lens barrel 1 and at which the optical axis a10 is located.

Although FIG. 13 illustrates the first lens barrel 1 being disengagedfrom the second lens barrel in order to clearly show how the firstadjustment screw 41 and the second adjustment screw 42 relate to thefirst screw abutment face 1D and the second screw abutment face 1E, andhow the first adjustment spring 43 and the second adjustment spring 44relate to the first spring-pressed face 1F and the second spring-pressedface 1G; however, the first lens barrel 1 is actually inserted in thesecond lens barrel 2, and abutment or pressing according to eachassociation line shown in FIG. 13 occurs in this state.

FIG. 14 is a diagram showing how the second adjustment screw 42 may abutwith the second screw abutment face 1E, and how the second adjustmentspring 44 may press against the second spring-pressed face 1G. FIG. 15is a diagram showing the first adjustment screw 41 and second adjustmentscrew 42, the first adjustment spring 43A, the first spring retainer43B, the second loading spring 44A, and the second spring retainer 44Bhaving been installed, in a cross section along a direction which isorthogonal to the optical axis direction.

As shown in FIG. 13, FIG. 14, and FIG. 15, the first screw abutment face1D, the second screw abutment face 1E, the first spring-pressed face 1F,and the second spring-pressed face 1G are provided in portions of theouter surface of the first lens barrel 1. These faces are orthogonal tothe axial directions of the first adjustment screw 41, the secondadjustment screw 42, the first loading spring 43A, and the secondloading spring 44A, respectively. As a result, it becomes possible toappropriately apply forces from the respective adjustment screws andloading springs to the first lens barrel 1.

The action of such structure will be described with reference to FIG. 1and FIG. 15. When the first adjustment screw 41, the second adjustmentscrew 42, the first loading spring 43A, and the second loading spring44A are installed in the first lens barrel 1 with appropriate abutmentand pressing, the position of the first unit 20 along the arrow D41Ldirection and the arrow D42L direction in FIG. 1 (the position of thefirst unit 10 with respect to the second unit 20 along a radialdirection) is uniquely determined. In this state, if the first unit 10is eccentric from the second unit 20 along the arrow D41L direction, anadjustment is made by rotating the first adjustment screw 41 in thearrow D41R direction as appropriate. Similarly, if it is eccentric inthe arrow D42L direction, an adjustment is made by rotating the secondadjustment screw 42 in the arrow D42R direction as appropriate. Thespring specifications are selected so that, as shown in FIG. 15, thefirst adjustment screw 41, the second adjustment screw 42, the firstloading spring 43A, and the second loading spring 44A always exert someforce in an arrow D41J direction, an arrow D42J direction, an arrow D43Jdirection, and an arrow D44J direction, respectively. This allows thefirst unit 10 to follow the movements which are caused by rotation ofthe first adjustment screw 41 and the second adjustment screw 42.

Moreover, as described above, the first adjustment screw 41 and thesecond adjustment screw 42 are orthogonal to each other, and the firstscrew abutment face 1D and the second screw abutment face 1E areorthogonal to each other; therefore, adjustments via the firstadjustment screw 41 and the second adjustment screw 42 functionindependently, so that a positional adjustment along a direction A1 anda positional adjustment along a direction A2 in FIG. 15 can be madeindependently.

Furthermore, the pressurizing bulge 41T and the pressurizing bulge 42Tof the first adjustment screw 41 and the second adjustment screw 42 havehemispheric surface shapes, thus resulting in point contact existingbetween the first screw abutment face 1D and the second screw abutmentface 1E. As a result of this, even when adjustments made via the firstadjustment pin 31, the second adjustment pin 32, and the thirdadjustment pin 33 introduce changes in the angles of contact between thefirst adjustment screw 41 and the first screw abutment face 1D andbetween the second adjustment screw 42 and the second screw abutmentface 1E as described above, the first lens barrel 1 is allowed toundergo smooth angular changes relative to the second lens barrel 2.

With the above construction, any tilt of the optical axis, the positionalong the optical axis direction, and the radial deviation of the firstunit 10 relative to the second unit 20 can be reliably adjusted, basedon a simple construction.

In the above construction, after completion of adjustments, the firstunit 10 and the second unit 20 may be fixed with an adhesively bond orthe like; doing so will allow the first adjustment pin 31, the secondadjustment pin 32, the third adjustment pin 33, the first adjustmentscrew 41, the second adjustment screw 42, the first loading spring 43A,the second loading spring 44A, the third loading spring 45A, the firstspring retainer 43B, the second spring retainer 44B, and the thirdspring retainer 45B to be eventually removed from the completed lensunit 100. Alternatively, after completion of the above adjustments, inorder to prevent the first adjustment pin 31, the second adjustment pin32, the third adjustment pin 33, the first adjustment screw 41, and thesecond adjustment screw 42 from pivoting, these adjustment pins andadjustment screws may be fixed to the second lens barrel 2 with anadhesive or the like.

Note that the shapes of the adjustment pins and adjustment screws in theabove embodiment are exemplary; the adjustment pins and adjustmentscrews may have other shapes. For example, FIGS. 16( a), (b), and (c)show a perspective view, a front view, and a cross-sectional view of afirst adjustment pin 31′, a second adjustment pin 32′, and a thirdadjustment pin 33′ having a different shape from that in the aboveembodiment.

Each of the first adjustment pin 31′, the second adjustment pin 32′, andthe third adjustment pin 33′ has a guide axis portion 3A, an eccentricportion 3B′, and a manipulating portion 3C. As shown in FIG. 16( c), theeccentric portion 3B′ has an axis center which is tilted with respect tothe guide axis center of the guide axis portion 3A. Therefore, a tip 3Dof the eccentric portion 3B′ has an eccentric axis which is eccentricfrom the guide axis center.

FIGS. 17( a) and (b) are a side view and a cross-sectional view of alens unit 100′ in which the first adjustment pin 31′, the secondadjustment pin 32′, and the third adjustment pin 33′ are used. Similarlyto the above embodiment, the first adjustment pin 31′, the secondadjustment pin 32′, and the third adjustment pin 33′ are supported so asto be capable of rotating, by a first guide hole 2A, a second guide hole2B, and a third guide hole 2C which are provided in the second lensbarrel 2. Moreover, the eccentric portions 3B′ and the tips 3D of thefirst adjustment pin 31′, the second adjustment pin 32′, and the thirdadjustment pin 33′ are respectively inserted in the first adjustmentgroove 1A, the second adjustment groove 1B, and the third adjustmentgroove 1C.

The first adjustment pin 31′, the second adjustment pin 32′, and thethird adjustment pin 33′ having such structure function in similarmanners to the first adjustment pin 31, the second adjustment pin 32,and the third adjustment pin 33 described in the above embodiment, andcan be suitably employed in the lens unit 100 of the above embodiment,instead of the first adjustment pin 31, the second adjustment pin 32,and the third adjustment pin 33.

FIGS. 18( a), (b), and (c) show a perspective view, a front view, and across-sectional view of a first adjustment pin 31″, a second adjustmentpin 32″, and a third adjustment pin 33″ having a different shape fromthat in the above embodiment. As shown in these figures, each of thefirst adjustment pin 31″, the second adjustment pin 32″, and the thirdadjustment pin 33″ has a guide axis portion 3A, a manipulating portion3C, and a tip 3E. The tip 3E has a conical side face with a crosssection which decreases away from the guide axis portion 3A and towardthe leading end. The axis center of the tip 3E coincides with, and isnot eccentric from, the guide axis center of the guide axis portion 3A.The side face of the guide axis portion 3A is ridged.

FIGS. 19( a), (b), and (c) are a perspective view, a side view, and across-sectional view of a lens unit 100″ in which the first adjustmentpin 31″, the second adjustment pin 32″, and the third adjustment pin 33″are used. In the case of using the first adjustment pin 31″, the secondadjustment pin 32″, and the third adjustment pin 33″, it is preferablethat the lens unit 100″ further includes springs 51 both of whose endsare connected to the first lens unit 10 and the second lens unit 20 topress the first lens unit 10 toward the second lens unit 20, as anadjustment mechanism. Moreover, the first guide hole 2A, the secondguide hole 2B, and the third guide hole 2C (FIG. 6) which are providedin the second lens barrel 2 in order to support the first adjustment pin31″, the second adjustment pin 32″, and the third adjustment pin 33″ arepreferably threaded.

As shown in FIG. 19( c), the tips 3D of the first adjustment pin 31″,the second adjustment pin 32″, and the third adjustment pin 33″ areinserted in the first adjustment groove 1A, the second adjustment groove1B, and the third adjustment groove 1C, such that the conical side facesof the tips 3D abut with the side walls of these adjustment grooves.Depending on the amounts of insertion of the first adjustment pin 31″,the second adjustment pin 32″, and the third adjustment pin 33″ into thefirst adjustment groove 1A, the second adjustment groove 1B, and thethird adjustment groove 1C, the positions at which the tips 3D abut withthe adjustment grooves will change. Consequently, as has been describedin the above embodiment with reference to FIG. 12, if only one of thefirst adjustment pin 31″, the second adjustment pin 32″, and the thirdadjustment pin 33″ is individually rotated along the arrow D31Rdirection, the arrow D32R direction, or the arrow D33R direction, thefirst adjustment groove 1A will move along the arrow D31L direction, thesecond adjustment groove 1B along the arrow D32L direction, and thethird adjustment groove 1C along the arrow D33L direction, each alone byitself. As a result of this, the first unit 10 will be tiltedrespectively in the arrow D31T direction, the D32T direction, or theD33T direction. By utilizing this principle, the tilting angle of theoptical axis a10 of the first unit 10 with respect to the optical axisa20 of, the second unit 20 can be adjusted.

In the present embodiment, it is assumed that necessary adjustmentmargins in relation to the optical axis tilt, axial position, and radialdeviation of the first unit 10 relative to the second unit 20 areprovided between the two.

Although the above embodiments illustrate three lens and two lensesbeing respectively installed in the first unit 10 and the second barrel2, it will be appreciated that the effects of the present invention canbe obtained without being limited to such numbers of lenses.

In every embodiment described above, similar effects can be obtainedwhether resin or glass is used as the material composing the lenses.However, when the lenses are glass, the lens barrel may be metal; whenthe lenses are resin, the lens barrel may also be resin; in this manner,the difference in coefficient of linear expansion between the two can bereduced, which is preferable in terms of reducing deformation due to adifference between their amounts of deformation caused by temperaturechanges.

As for any of the lenses, the shape of the optically effective surfaceis not limited to the shape shown in the respective drawing, and yeteffects of the present invention can be obtained.

Although the above embodiments illustrate the present invention bytaking a lens unit with a fixed magnification as an example, the presentinvention can also be suitably used for a lens unit having a zoomingfunction.

In the above embodiments, the adjustment mechanism of the lens unitincludes adjustment pins for adjusting relative positioning along theoptical axis direction and tilt between respective optical axes of thefirst lens barrel and the second lens barrel, and adjustment screws foradjusting their mutual radial deviation. Depending on the lenscharacteristics, the structure of the barrels into which lenses areinstalled, and the application of the lens unit, an adjustment mechanismmay be provided for adjusting at least one of: relative positioningalong the optical axis direction, tilt between respective optical axes,and mutual radial deviation of the first lens barrel and the second lensbarrel. Moreover, screws may be provided on the adjustment pins foradjusting relative positioning along the optical axis direction and tiltbetween respective optical axes of the first lens barrel and the secondlens barrel, such that the tips of the adjustment pins will abut alsowith the bottoms of the adjustment grooves, thus conferring to theadjustment pins a function of adjusting mutual radial deviation of theoptical axes.

INDUSTRIAL APPLICABILITY

A lens unit according to the present invention is to be used for acamera or the like, and is useful in the case where high precision isrequired for the respective errors of positioning along the optical axisdirection, tilt, or radial deviation of lenses which are installed in alens barrel.

REFERENCE SIGNS LIST

-   -   1 first lens barrel    -   1A first adjustment groove    -   1B second adjustment groove    -   1C third adjustment groove    -   1D first screw abutment face    -   1E second screw abutment face    -   1F first spring-pressed face    -   1G second spring-pressed face    -   1R alignment guide recess    -   10 first barrel    -   11 first lens    -   12 second lens    -   13 third lens    -   2 second lens barrel    -   2A first guide hole    -   2B second guide hole    -   2C third guide hole    -   2D first adjustment screw hole    -   2E second adjustment screw hole    -   2F first spring fixing hole    -   2G second spring fixing hole    -   2R alignment bump    -   20 second barrel    -   24 fourth lens    -   25 fifth lens    -   26 spacer    -   27 lens retainer    -   31 first adjustment pin    -   32 second adjustment pin    -   33 third adjustment pin    -   3A guide axis portion    -   3B eccentric portion    -   3C manipulating portion    -   41 first adjustment screw    -   41T pressurizing bulge    -   42 second adjustment screw    -   42T pressurizing bulge    -   43A first loading spring    -   43B first spring retainer    -   44A second loading spring    -   44B second spring retainer

The invention claimed is:
 1. A lens unit comprising: a first lens groupand a second lens group being disposed in series on a same optical axisto have a light-converging function, the first lens group and the secondlens group each including at least one lens; a first lens barrelretaining the first lens group; a second lens barrel retaining thesecond lens group and encasing at least a portion of the first lensbarrel; and an adjustment mechanism provided in a region of the firstlens barrel and the second lens barrel where the second lens barrelencases at least a portion of the first lens barrel, the adjustmentmechanism being for adjusting: relative positioning along an opticalaxis direction, tilt between respective optical axes, and mutual radialdeviation, of the first lens barrel and the second lens barrel, wherein,for adjusting the relative positioning along the optical axis directionand the tilt between the respective optical axes, the adjustmentmechanism includes three adjustment pins supported so as to be capableof pivoting on an outer surface of the second lens barrel, and threeadjustment grooves being located on an outer surface of the first lensbarrel and extending along a circumferential direction of the outersurface; each of the three adjustment pins includes a guide axis portionof a cylindrical shape whose center defines a guide axis center aroundwhich the pivoting is to occur, and an eccentric portion having aneccentric axis center which is eccentric from the guide axis center andhaving, in at least a portion thereof, a circular cross section centeredaround the eccentric axis center, the guide axis portion being insertedin a guide hole so as to be capable of pivoting, the guide hole havingan axis center along a radial direction of the second lens barrel, andthe eccentric portion of each of the three adjustment pins being engagedin a respective one of the three adjustment grooves of the first lensbarrel; for adjusting mutual radial deviation between the first lensbarrel and the second lens barrel, the adjustment mechanism furtherincludes two adjustment screws and two loading springs, the twoadjustment screws being supported by the second lens barrel so as to becapable of pivoting, and the two adjustment screws, respectively, andthe two loading springs, respectively, being located on two linesorthogonally intersecting at a point on a plane which is perpendicularto the optical axis of the first lens barrel and at which the opticalaxis is located; each of the two adjustment screws includes a ridgedscrew portion, a screw head portion located at one end along an axialdirection, and a pressurizing bulge located at another end along theaxial direction, the screw portion being screwed into a screw hole, anaxial direction of the screw hole being a radial direction in a crosssection of the second lens barrel that is perpendicular to the opticalaxis, and the pressurizing bulge abutting against a screw abutment faceprovided on an outer surface of the first lens barrel, the screwabutment face being orthogonal to an axis center of the adjustmentscrew; each of the two loading springs is coaxial with a correspondingone of the two adjustment screws supported by the second lens barrel,and presses the first lens barrel from the second lens barrel toward theoptical axis of the first barrel; and the screw abutment faces againstwhich the two adjustment screws respectively abut are orthogonal to eachother.
 2. The lens unit of claim 1, wherein, the three adjustment pinsare disposed on an outer surface of the second lens barrel at aninterval of 120 degrees centered around the optical axis.
 3. The lensunit of claim 1, wherein, when the three adjustment pins aresimultaneously pivoted in a same direction and with a same velocity, thefirst lens barrel is moved relative to the second lens barrel inparallel to the optical axis direction; and when at least one of thethree adjustment pins is pivoted in a different direction or with adifferent velocity from that of any other, the optical axis of the firstlens barrel is tilted with respect to the optical axis of the secondlens barrel.
 4. The lens unit of claim 1, wherein the eccentric portionof each adjustment pin has a bloated barrel surface in at least aportion thereof, the eccentric portion achieving point contact with theadjustment groove at a portion of the bloated barrel surface.
 5. Thelens unit of claim 1, wherein the first lens barrel moves relative tothe second lens barrel in a direction in which the adjustment screwproceeds when the adjustment screw is pivoted in the screw hole.
 6. Thelens unit of claim 1, wherein, the pressurizing bulge of each adjustmentscrew has a hemispheric portion, the hemispheric portion abuttingagainst the screw abutment face; and the first lens barrel movesrelative to the second lens barrel in a direction in which theadjustment screw proceeds when the adjustment screw is pivoted in thescrew hole.
 7. The lens unit of claim 1, wherein, among tolerances inlens assembly concerning an entire lens optics including the first lensgroup and the second lens group, a tolerance in assembly for satisfyinga required performance between a lens of the first lens group installedin the first lens barrel that is located the closest to the second lensbarrel and a lens of the second lens group installed in the second lensbarrel that is located the closest to the first lens barrel is smallerthan a tolerance in assembly between any other lenses.